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ARTHUR E. HEALY, OF NEW YORK, N. Y.

IMPRESSION COMPOSITION.

No Drawing.

To all whom it may concern:

Be it known that I, ARTHUR E. HEALY,

. "a citizen of the United States, and a resident of the city of New York, borough of Brooklyn, in the county of Kings and State of New York, have invented a new and Improved Impression Composition, of which the following is a full,clear, and exact de scription. a y

The invention relates to an impression composition adapted to be used by dentists and others, and has to deal more particularly with impression material of the plastic type which hardens by setting, to form a mold from which a cast or model is made.

According to present practice in dentistry the impression material is of. such a nature that it is diflicult to separate the mold from the cast without liability of injuring the 2 latter, since it is necessary to cut away the mold with a knife or other instrument, whereby the cast or model is often scarred or scratched, and as a consequence a new impression must be taken and another cast made.

The objects of the present invention are to overcome these difficulties by providing an impression material which can be readily separated from the cast or model without damaging the latter and with all the fine lines and parts of the impression reproduced in the model or cast, these results being attained by the following use of a process which is extremely simple and reliable.

In carrying out the invention the impression material is of such a nature that in making an impression it is handled in the usual manner, but after the cast or model is made the latter is separated from the mold or ma- 40 trix which bears the impression desired, by

the cast and mold being placed in boiling water, which has the effect of disintegratmg the impression material so as to leave the cast absolutely clean, with the impression 45 accurately and finely reproduced.

The impression material consists of plaster of Paris which forms the base, and mixed with this is a suitable material which cooperates with the plaster of Paris to form a p mixture that is more plastic than the plaster alone when mixed with cold or tepid water, and which will set in a few minutes after being applied to the part of which an impression is to be taken, and when a plaster of Paris cast or model is made from the mold thus formed, the mass can be placed in boil- .JPatented Aug. 8, 1916.

Application filed February 19, 1915. Serial No. 9,303.

ing hot water to cause the disintegration of .the mold, this disintegration being accomplished by the great expansion of the material mixed with the plaster of Paris in the mixed with the plaster of Paris may be rice flour, cornstarch, washmg starch, sodium chlorld, coloring matter, such as Vermilion,

and flavoring material, such as synthetical oil of Wintergreen, which ingredients are mixed in the substantial proportions as follows: plaster of Paris 50 lbs, rice flour 6 lbs, cornstarch 6 lbs., washing starch 2 lbs, sodium chlorid 1 1b., color (Vermilion) 1 oz., flavor (synthetical oil of Wintergreen) 3 fluid oz. These materials are mixed together and form a powder, and to render it usable for making a mold or matrix the powder is mixed in cold or tepid water in such quantity as to be of thick, creamy con sistency. It is now ready for the impression to be taken, and if used in dentistry this plastic material is applied to a tray and introduced into that part of the mouth of which an impression is to be taken, and there it is allowed to set from three to five minutes, depending on the body temperature and atmospheric conditions. After the material has been allowed to set it is re moved from the mouth and dried, when a suitable separating fluid is applied to the surface of the impression, and then the cast material, which is plaster of Paris, is poured into the mold or matrix. After this'hardens the tray is removed and the mass or block is trimmed of all unneeded surplus. The next step consists in introducing the mass formed by the mold and cast into boiling water, where it remains from three to eight minutes. The effect of this is that the mold or matrix made of the impression material separates itself from the model or cast by a disintegrating action, leaving the cast clean and perfect.

The composition of the plastic material is such that it is more plastic than impression material made of plaster of Paris, owing to the starchy ingredients. Because of these ingredients the composition when mixed with cold or tepid water has a negligible coefficient of expansion or contraction, and therefore the material is ideal for impression work. Due, however, to the starchy ingredients there will be a great expansion of the particles of the mold when the latter and cast are placed in boiling Water, and this expansion results in the dis integration of the mold, whereby the cast is finally left clean and free from adhering impression material.

' Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. .An impression material comprising a mixture of plaster of Paris and starchy material in the proportions of approximately four to one, and sodium chlorid in the approximate proportion by Weight of one'unit of sodium chlorid to fifty units of plaster of Paris.

2. An impression material comprising a mixture of plaster of Paris and starchy material in the proportions of approximately four to one, and sodium chlorid in the approximate proportion by Weight of one unit of sodium chlorid to fifty units of plaster of Paris, and a suitable quantity of flavoring and coloring material.

3. A composition for impression material, consisting of plaster of Paris 50 lbs., rice flour 6 lbs., cornstarch 6 lbs, Washing starch 2 lbs., sodium chlorid 1 1b., color (Vermilion) 1 oz., flavortsynthetical oil of Wintergreen) fiuid oz.

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses.

ARTHUR E. HEALY. Witnesses:

O. BRADWAY, PHILIP D. RoLLHAUs.

, Copies of this patent maybe obtained for five cents each, by addressing the Commissioner of Patents, Washington, D, 0. 

